Stereoselective access to either E- or Z-cyclic alkenes remains a formidable challenge. Now it has been shown that Pd-catalysed formal cycloaddition can lead to the construction of 11-membered heteroc...

We describe using a dynamically self-assembled octa-imine cage as a molecular flask to accelerate a bimolecular Diels–Alder reaction. We investigate the cage’s binding properties using 1H NMR spectroscopic titrations, ITC experiments, and X-ray crystallography. We detect and characterize the formation of the ternary complex (Michaelis) in solution. A detailed kinetic analysis of the reaction data supports that the cage’s acceleration is provided by including the two reactants, resulting in an effective molarity (EM) of ∼40 M. Exo-selectivity and shift of the reaction’s chemical equilibrium are also encountered in the cage’s confined space. Our results mimic enzymes’ ability to bind two substrates in a polar cavity, using directional interactions, and accelerate their stereoselective reaction, with the potential for cavity engineering to enable other reactions.

Nitric oxide (NO) was efficiently converted to molecular nitrogen (N2) in an acidic aqueous solution containing iron(III) porphyrin encapsulated in the cyclodextrin (CD) nanocavity. The supramolecular...

Diterpene alkaloids have fascinated the synthetic community for well over half a century and have long documented use in the treatment of pain and other ailments. Recently Shi and Zhang isolated a new class of sulfonated diterpene alkaloids from the roots of Aconitum carmichaelii. These zwitterionic alkaloids possess several unprecedented new ring systems and displayed potent analgesic properties in preliminary pain model studies in mice. Herein we describe synthetic entry into this subclass of C20 diterpene alkaloids via a total synthesis of the most potent analgesic member aconicarmisulfonine A, which features an unusual sulfonated bicyclo[3.3.1]nonane core. Key synthetic maneuvers include a Ir-catalyzed caprolactam synthesis, a stereoselective Mannich cyclization, and a highly diastereoselective Mukaiyama–Michael cascade. A late-stage thiol to sulfonate oxidation completed the synthesis.

The catalytic construction of carbon–carbon bonds in small organic molecules via chain walking is described. Catalytic cycloisomerization of 1,n-dienes via chain walking was achieved using a palladium...

A secondary phosphine oxide (SPO) unit has been grafted on an inherently chiral calixarene, providing four stereoisomers that were separated by chiral HPLC. These low-symmetry ligands were then used i...

We describe the quantitative self-assembly (>90%) of a [4 + 2] octa-imine cage (1) in a CDCl3:CD3CN 9:1 solvent mixture containing 0.5% of acetic acid. Cage 1 is based on two identical aryl-extended calix[4]pyrrole units linked through eight dynamically reversible imine bonds. Cage 1 forms thermodynamically and kinetically highly stable inclusion complexes featuring 1:1 and 2:1 stoichiometry with suitable para-substituted pyridine-N-oxides. The ability of 1 for the pairwise inclusion of two different pyridine-N-oxides led us to investigate its properties as a reactor vessel. The coinclusion of 4-azido pyridine-N-oxide and 4-ethynyl pyridine-N-oxide did not produce a detectable acceleration of their 1,3-dipolar cycloaddition reaction. Conversely, the coinclusion in cage 1 of the same alkyne dipolarophile with 4-azido(alkyl) pyridine-N-oxides (alkyl= methyl, ethyl) produced significant reaction acceleration. We quantified the reactions’ acceleration with an effective molarity (EM) of ∼103 M, corresponding to the more prominent reported value of a bimolecular 1,3-dipolar cycloaddition reaction in a molecular vessel by directly detecting the ternary Michaelis complex. The included reactions are quantitative and regioselective, yielding exclusively the 1,4-disubstituted triazole isomers. We propose that the selectivity of 1 in accelerating the included 1,3-dipolar cycloadditions is related to (a) the entropy gain provoked by the reaction’s inclusion, (b) the rigidity of the container, and (c) the spatial fixation of the polar knobs (pyridine-N-oxide) carrying the reacting groups in its two functionalized hemispheres. The two latter characteristics render the distance between the reacting groups (azido and ethynyl) almost fixed by design, thus allowing or not achieving the transition state’s geometry. We support our hypothesis with the help of DFT calculations of the inclusion complexes’ structures.

Discovering hydrogen evolution reaction (HER) catalysts is challenging yet vital for energy and potentially synthesis. Here alkali metal–cobalt Salen systems with high HER activity is developed and is...

A [2]catenane-based receptor functionalized with stiff-stilbene can be reversibly switched with 340/385 nm light between its Z- and E-isomers, which leads to a considerable change in chloride binding ...

The enantioselective epoxidation of naphthalenes into their corresponding arene oxides with aqueous hydrogen peroxide is described. The reaction combines dearomatization with installation of chemical...

Electrostatic interactions, hydrogen bonding, and solvation effects can alter the free energies of ionizable functional groups in proteins and other nanoporous architectures, allowing such structures to tune acid–base chemistry to support specific functions. Herein, we expand on this theme to examine how metal sites (M = H2, ZnII, CoII, CoI) affect the pKa of benzoic acid guests bound in discrete porphyrin nanoprisms (M3TriCage) in CD3CN. These host–guest systems were chosen to model how porous metalloporphyrin electrocatalysts might influence H+ transfer processes that are needed to support important electrochemical reactions (e.g., reductions of H+, O2, or CO2). Usefully, the cavities of the host–guest complexes become hydrated at low water concentrations (10–40 mM), providing a good representation of the active sites of porous electrocatalysts in water. Under these conditions, Lewis acidic CoII and ZnII ions increase the Bro̷nsted acidities of the guests by 4 and 8 pKa units, respectively, while reduction of the CoII sites to anionic CoI sites produces an electrostatic potential that lowers acidity by ca. 4 units (8 units relative to the CoII state). Lacking functional metal sites, H6TriCage increases the acidity of the guests by just 2.5 pKa units despite the 12+ charge of this host and contributions from other factors (hydrogen bonding, hydration) that might stabilize the deprotonated guests. Thus, the metal sites have dominant effects on acid–base chemistry in the M3TriCages, providing a larger pKa range (12.75 to ≥24.5) for an encapsulated acid than attained via other confinement effects in proteins and artificial porous materials.

Investigating stimulus-responsive structural transformations of complex mechanically interlocked molecules (MIMs) is key to better understanding the dynamic behaviors of biological macromolecules. Her...

Reversible and unidirectional expansion of an acicular porous molecular crystal is observed with gas uptake. Using in situ structural and photomicrographic techniques, a molecular-level insight is obt...

The first heterometallic Pt(II)–Pd(II) quadruply interlocked cage catenane (Pt2Pd2L8) has been assembled via a combination of metal-mediated self-assembly and dynamic covalent chemistry. The integrat....

Through imine condensation, a tetrahedral cage-shaped molecule was obtained in a one-pot manner, which comprises four trisamino vertices and four trisformyl faces each containing three meta-methyl-pyr...

Here, a [3 + 10] non-closed macrocycle was serendipitously self-assembled, incorporating two monovalent diamines, each with an unreacted amino group. These are selectively removed via imine exchange, ...

A new active metal template synthesis of [2]rotaxanes is described. We demonstrate the use of macrocyclic BINOL-phosphates as ligands for the Cu(I)-mediated alkyne-azide cycloaddition, establishing a ...

Medical devices are generally made of polyvinyl chloride plasticized by six authorized plasticizers as alternatives to di-(2-ethylhexyl)-phthalate (DEHP) classified as reprotoxic class 1b. These are a...

An overcrowded ethylene composed of electron-donating anion and electron-accepting cation shows multiple NIR chromisms accompanying the conformational change between folded and twisted conformers. Th...

In multimetallic compounds, N2 typically bridges late transition metals in an end-on (η1:η1) fashion while early transition metals often bind N2 side-on (η2), with the latter resulting in more significant N–N bond elongation. Herein, N2 fixation is accomplished by using a well-defined scaffold featuring a heterobimetallic combination of Zr and Co. We report a heterotetrametallic Zr2Co2 cluster in which N2 is bound side-on to the two Co centers and end-on to Zr in a μ3-η1:η2:η2 binding mode that defies established paradigms for N2 binding. The heterometallic approach is shown to facilitate catalytic reductive silylation of N2 with turnover numbers far exceeding those of reported cobalt catalysts.

Reductive N2 cleavage at an acridane PNP pincer-supported Mo center leads to the first crystallographically characterized example of an unusual Mo(IV) nitride species featuring a bridging N2 coordina...

Although various skeletons of organic ligands have been applied to achieve the structural diversity of metallasupramolecular assemblies, limited approaches are available for organometallic cluster-bas...

Pumping ions against a concentration gradient through protein-based transporters is a cornerstone of numerous biological processes. Mimicking this function by using artificial receptors remains a daun...

Humanity’s replacement of fossil-fuel energy with renewable electricity will require extensive deployment of lithium batteries, which necessitates an increase in the rate of production of this vital metal. Current extraction methods from brines and ores are very energy-intensive, as are recycling methods. Here we report a novel Li5L2 sandwich structure in which five lithium ions are bound between the azobipyridine groups of two pentagonal ligands. The geometry of these ligands leads to the selectivity for binding Li+ in the presence of Na+ and K+. Upon illumination, the trans-azobipyridine moieties of the ligands isomerize to their cis form, promoting the release of free Li+ as the sandwich comes apart. The selective complexation of Li+, and its photostimulated release, were used as the basis of a cycle for selectively extracting and releasing Li+ ions from a mixture with Na+ and K+. Solar energy may thus be used directly to purify this metal, which is essential for storing increasingly cheap electricity produced through renewable means.

Wacker oxidation is widely used to convert alkenes to carbonyls, but selective oxidation of unbiased internal alkenes can be difficult. Here a nickel-catalyzed alkene isomerisation-oxidation strategy ...

Tubular structures with nanosized pores have shown remarkable applications in areas such as ion transport and water filtration, but their development is often hindered by challenges including low yiel...